Toán Lớp 6: tìm x,y thuộc biết a, ( x + 5) . ( y -3 ) = 15

Question

Toán Lớp 6:  tìm x,y thuộc biết a, ( x + 5) . ( y -3 ) = 15

thaolanphuobg · Answer

Answer    $ text{V&igrave;}$ x , y  in ZZ $ text{n&ecirc;n}$ x + 5 ; y - 3  in ZZ   => (x + 5) . (y - 3)  in Ư(15) = {+-1 ; +-3 ; +-5 ; +-15}   $ text{Lập bảng gi&aacute; trị:}$    $ begin{array}{|c|c|c|} hline x + 5&1&3&5&15&-1&-3&-5&-15   hline y-3&15&5&3&1&-15&-5&-3&-1   hline x&-4&-2&0&10&-6&-8&-10&-20   hline y&18&8&6&4&-12&-2&0&2   hline  text{Thử lại}& text{TM}& text{TM}& text{TM}& text{TM}& text{TM}& text{TM}& text{TM}& text{TM}   hline end{array}$    $ text{Vậy}$ (x , y) = (-4 , 18) ; (-2 , 8) ; (0 , 6) ; (10 , 4) ; (-6 , -12) ; (-8 , -2) ; (-10 , 0) ; (-20 , 2)

huenthanh97 · Answer

$ ( x + 5 ) . ( y - 3 ) = 15 $      $ TH1 : $  ( left[  begin{array}{l}x+5=5  y-3=3 end{array}  right. )      $ &rArr; $  ( left[  begin{array}{l}x=0  y=6 end{array}  right. )      $ TH2 : $  ( left[  begin{array}{l}x+5=3  y-3=5 end{array}  right. )      $ &rArr; $  ( left[  begin{array}{l}x=-2  y=8 end{array}  right. )      $ TH3 : $  ( left[  begin{array}{l}x+5=-3  y-3=-5 end{array}  right. )      $ &rArr; $  ( left[  begin{array}{l}x=-8  y=-2 end{array}  right. )      $ TH4 : $  ( left[  begin{array}{l}x+5=-5  y-3=-3 end{array}  right. )      $ &rArr; $  ( left[  begin{array}{l}x=-10  y=-6 end{array}  right. )      $ TH5 : $  ( left[  begin{array}{l}x+5=15  y-3=1 end{array}  right. )      $ &rArr; $  ( left[  begin{array}{l}x=10  y=4 end{array}  right. )      $ TH6 : $  ( left[  begin{array}{l}x+5=1  y-3=15 end{array}  right. )      $ &rArr; $  ( left[  begin{array}{l}x=-4  y=18 end{array}  right. )      $ TH7 : $   ( left[  begin{array}{l}x+5=-15  y-3=-1 end{array}  right. )      $ &rArr; $  ( left[  begin{array}{l}x=-20  y=2 end{array}  right. )      $ TH8 : $  ( left[  begin{array}{l}x+5=-1  y-3=-15 end{array}  right. )      $ &rArr; $  ( left[  begin{array}{l}x=-6  y=-12 end{array}  right. )